Uniqueness of infrared asymptotics in Landau gauge Yang-Mills theory

We uniquely determine the infrared asymptotics of Green functions in Landau gauge Yang-Mills theory. They have to satisfy both, Dyson-Schwinger equations and functional renormalisation group equations. Then, consistency fixes the relation between the infrared power laws of these Green functions. We discuss consequences for the interpretation of recent results from lattice QCD.Comment: 24 pages, 8 figure

Biogeographic partitioning and host specialization among foraminiferan dinoflagellate symbionts ( Symbiodinium

Large discoidal soritid foraminiferans (Soritinae) are abundant in coral reef ecosystems. As with the many cnidarian invertebrates that inhabit these systems, they also depend on symbiotic dinoflagellates (Symbiodinium) for their growth and survival. Several particular Symbiodinium sub-genera or clades inhabit these soritids. One of these groups, referred to as cladeC, dominates corals and their relatives throughout the tropical Indo-Pacific. In contrast, the distributions of Symbiodinium spp. from cladesA, B, and C are more evenly apportioned across Caribbean invertebrate communities. To explore the possibility that a similar biogeographic break exists in the symbionts harbored by soritids, we surveyed the Symbiodinium spp. from the soritid genus Sorites, collected from the Pacific and Caribbean coasts of Panama as well as from Florida. Characterization of Symbiodinium obtained from foraminiferal and cnidarian samples was conducted using restriction fragment length polymorphism and phylogenetic analyses of the nuclear internal transcribed spacer region2 (ITS2) and a portion of the large subunit ribosomal DNA sequences. A distinctive biogeographic break between the kinds of symbionts found in Sorites from the East Pacific and Caribbean was clearly evident. Differences between cnidarian and foraminferan symbioses in each ocean may be explained by the subjection of Caribbean communities to severer environmental conditions during the early Quarternary. Caribbean Sorites spp. harbored symbionts described from cladeF (specifically sub-cladeFr4) and cladeH (formally referred to as Fr1), while Sorites spp. from the eastern Pacific were dominated by a single Symbiodinium haplotype in cladeC. An ITS2 phylogeny determined that most cladeC "types” recovered from Indo-Pacific soritids form a monophyletic sub-lineage with other cladeC symbionts typically found in Pacific corals from the genus Porites. The existence of multiple Symbiodinium lineages at various taxonomic levels associated specifically with soritids indicates that symbioses with these hosts are important in driving Symbiodinium spp. evolutio

Sarma phase in relativistic and non-relativistic systems

We investigate the stability of the Sarma phase in two-component fermion systems in three spatial dimensions. For this purpose we compare strongly-correlated systems with either relativistic or non-relativistic dispersion relation: relativistic quarks and mesons at finite isospin density and spin-imbalanced ultracold Fermi gases. Using a Functional Renormalization Group approach, we resolve fluctuation effects onto the corresponding phase diagrams beyond the mean-field approximation. We find that fluctuations induce a second order phase transition at zero temperature, and thus a Sarma phase, in the relativistic setup for large isospin chemical potential. This motivates the investigation of the cold atoms setup with comparable mean-field phase structure, where the Sarma phase could then be realized in experiment. However, for the non-relativistic system we find the stability region of the Sarma phase to be smaller than the one predicted from mean-field theory. It is limited to the BEC side of the phase diagram, and the unitary Fermi gas does not support a Sarma phase at zero temperature. Finally, we propose an ultracold quantum gas with four fermion species that has a good chance to realize a zero-temperature Sarma phase.Comment: version published in Phys.Lett.B; 10 pages, 5 figure

Anti-deSitter universe dynamics in LQC

A model for a flat isotropic universe with a negative cosmological constant $\Lambda$ and a massless scalar field as sole matter content is studied within the framework of Loop Quantum Cosmology. By application of the methods introduced for the model with $\Lambda=0$, the physical Hilbert space and the set of Dirac observables are constructed. As in that case, the scalar field plays here the role of an emergent time. The properties of the system are found to be similar to those of the $k=1$ FRW model: for small energy densities, the quantum dynamics reproduces the classical one, whereas, due to modifications at near-Planckian densities, the big bang and big crunch singularities are replaced by a quantum bounce connecting deterministically the large semiclassical epochs. Thus in Loop Quantum Cosmology the evolution is qualitatively cyclic.Comment: Revtex4, 29 pages, 20 figures, typos correcte

Concept of Formation Length in Radiation Theory

The features of electromagnetic processes are considered which connected with finite size of space region in which final particles (photon, electron-positron pair) are formed. The longitudinal dimension of the region is known as the formation length. If some external agent is acting on an electron while traveling this distance the emission process can be disrupted. There are different agents: multiple scattering of projectile, polarization of a medium, action of external fields, etc. The theory of radiation under influence of the multiple scattering, the Landau-Pomeranchuk-Migdal (LPM) effect, is presented. The probability of radiation is calculated with an accuracy up to "next to leading logarithm" and with the Coulomb corrections taken into account. The integral characteristics of bremsstrahlung are given, it is shown that the effective radiation length increases due to the LPM effect at high energy. The LPM effect for pair creation is also presented. The multiple scattering influences also on radiative corrections in a medium (and an external field too) including the anomalous magnetic moment of an electron and the polarization tensor as well as coherent scattering of a photon in a Coulomb field. The polarization of a medium alters the radiation probability in soft part of spectrum. Specific features of radiation from a target of finite thickness include: the boundary photon emission, interference effects for thin target, multi-photon radiation. The experimental study of LPM effect is described. For electron-positron colliding beams following items are discussed: the separation of coherent and incoherent mechanisms of radiation, the beam-size effect in bremsstrahlung, coherent radiation and mechanisms of electron-positron creation.Comment: Revised review paper, 96 pages, 28 figures. Description of SLAC E-146 experiment removed, discussion of CERN SPS experiment adde